This invention relates to an improvement in the packaging of canned goods and the like. More particularly, the invention relates to packaging of the type wherein the goods are wrapped under the tension in, usually, two sheets of plastic, the sheets usually being wrapped about the package at right angles to one another.
In a co-pending application Ser. No. 88,609 filed on Oct. 20, 1979 by Bernard R. Danti, such a package is described as being conveniently made of sheets of flexible films with secant modules of 1500 to 5000 psi. These films are extended, typically, 30% to 50% during a snug wrap procedure thereupon, then the film is then heatsealed and allowed to contract into a snug fit over the package. Unfortunately, extension to this degree during the wrapping procedure causes enough wrinkling of the film to either interfere with the efficacy of the heatseal procedure or to slow down the procedure to the point that commercial use of the process is limited.
These films are extended during a snug-wrap procedure. Thereupon, the resultant tension in the film is mechanically isolated from the area where heat sealing is to occur, e.g., by mechanical clamping. Residual tension is reduced to essentially zero in that the seal area by a number of means, e.g. changing web path length, for example, before the heat jaws are brought into contact with the film. All of the above must be accomplished in very little space so as to preserve the film extension introduced into the film initially.
Moreover, particularly packages as described in copending application Ser. No. 88,609 have 30-50% extension of the film bands in final form. Unfortunatley, these high stretch percentages cause high lateral contraction which results in severe wrinkling of the films so as to interfere with the heat sealing procedure described above in such fashion as to produce unacceptable packages, and machinery which is extremely complex, comprehensive, and slow in performance to the point that commercial use of the process is limited.
The package itself has so many benefits that it was desirable to seek an alternative packaging process.